Mechanical basis for the morphology of fibrillar aggregates

The self-assembly of fibrillar aggregates is of importance in biology, biomedicine and materials science, yet understanding the range of possible shapes for these structures remains an open question. We propose a coarse-grained approach that averages over specific molecular details to suggest that the spatial complexity of self-assembling fibrillar structures is due to the competing effects of (the bending and twisting) elasticity of individual filaments and the adhesive interactions between them. We show that a theoretical framework accounting for this allows us to capture a number of diverse fibril morphologies observed in natural and synthetic systems, ranging from Filopodia to multi-walled carbon nanotubes, and leads to a phase diagram of possible fibril shapes. We also show how the extreme sensitivity of these morphologies can lead to spatially chaotic structures. Together, these results suggest a common mechanical basis for the micronscale fibril morphology as a function of the nanoscale mechanical properties.